JP5732648B2 - Bidirectional optical module and optical pulse tester - Google Patents

Description

  The present invention relates to a bidirectional optical module, and more particularly to a bidirectional module used in an optical pulse tester used for measuring a break point of an optical fiber communication network.

  Optical communication systems and measuring devices such as optical fiber sensors using light include a light source that emits light and a light receiving unit that senses the light. A measuring instrument used for maintenance and management of an optical communication system includes a light source that emits measurement light to a measured optical fiber and a light receiving unit that senses the light transmitted by the measured optical fiber.

  For example, in an optical communication system that performs data communication or the like using an optical signal, an optical pulse called, for example, OTDR (Optical Time Domain Reflectometer) is used in laying or maintaining an optical fiber in order to monitor the state of the optical fiber that transmits the optical signal. A tester is used. The OTDR repeatedly inputs pulsed light into the optical fiber to be measured, and measures the level of the reflected light and backscattered light from the optical fiber to be measured and the light reception time, thereby causing disconnection or loss of the optical fiber to be measured. Measure the state.

  The optical pulse tester includes a bidirectional optical module, a Bi-Directional module, and the like, in which a transmission unit and a reception unit are housed in the same case and are modularized into one. These modules become low-priced with the recent spread of FTTH (Fiber To The Home), and are often used not only for OTDR but also for other measuring instruments and optical communication systems.

  For example, an OTDR using a bidirectional optical module includes a bidirectional optical module 1, an LD drive unit 2, a sampling unit 3, a signal processing unit 4, and a display unit 5, as shown in FIG. Composed.

  The bidirectional optical module 1 is a module that outputs pulsed light to the optical fiber 7a or 7b to be measured via the measurement connector 6a or 6b and senses return light from the optical fiber 7a or 7b. The LD driving unit 2 is a driving unit that drives a light source in the bidirectional optical module 1. The sampling unit 3 is a functional unit that converts an electrical signal (photocurrent) from a light receiving unit in the bidirectional optical module 1 into a voltage and samples it. The signal processing unit 4 is a functional unit that causes the bidirectional optical module 1 to output pulsed light via the LD driving unit 2 and causes the sampling unit 3 to perform sampling. Further, the signal processing unit 4 performs an arithmetic process on the electrical signal resulting from the sampling by the sampling unit 3. The display unit 5 is a functional unit that displays the signal processing result, and for example, a display or the like can be used.

  In general, the OTDR is a measuring instrument used at the site of laying construction and maintenance in order to grasp the length and connection point of an optical fiber and identify a faulty part such as a disconnection. In OTDR, communication wavelengths (for example, 1310 nm and 1550 nm) are used when an optical fiber is laid, and wavelengths other than the communication wavelength (for example, 1625 nm or 1650 nm, and below are used for maintenance and monitoring so as not to affect the communication wavelength during maintenance and monitoring. Are generally measured using a "maintenance wavelength"). The break point position in the line to be measured of the optical fiber can be acquired by a time difference from when the light source (for example, a semiconductor laser) emits pulsed light until the return light reflected at the break point reaches the light receiving unit.

  Here, as the performance at the time of maintenance / monitoring of OTDR, the wavelength at the time of holding / monitoring is a wavelength band that does not affect the wavelength of communication light, and can be measured normally even if communication light is input to OTDR. Is required. For this reason, the conventional OTDR is configured to use a cut filter that cuts off communication light so that the light can be cut and accurately measured even when light of the communication wavelength is input during maintenance and monitoring. In order to prevent erroneous connection, the OTDR generally has a configuration in which an optical output connector is separated by a communication wavelength and a maintenance wavelength and two output ports are provided. In the OTDR shown in FIG. 3, for example, the measurement connector 6a for outputting the pulsed light of the communication wavelength to the optical fiber 7a to be measured and the measurement connector 6b for outputting the pulsed light of the maintenance wavelength to the optical fiber 7b to be measured Has two output ports.

  Here, based on FIG. 4, the structure of the conventional bidirectional | two-way optical module 1 used for installation maintenance correspondence is demonstrated. The conventional bidirectional optical module 1 shown in FIG. 4 is an example of a pigtail type three-wavelength compatible module, which includes semiconductor lasers 11a to 11c, lenses 12a to 12c and 16, a WDM (Wavelength Division Multiplexing) coupler 13, and the like. , Optical couplers 14 and 19, WDM filter module 15, light receiving element 17, and BPF (Band-pass filter) module 18.

The semiconductor lasers 11a to 11c are light emitting elements that emit light. The semiconductor laser 11a is a wavelength lambda _1, the semiconductor laser 11b is a wavelength lambda _2, the semiconductor laser 11c emits light having a wavelength lambda _3. For example, the semiconductor lasers 11a and 11b emit light having a communication wavelength, for example, wavelengths 1310 nm and 1550 nm, and the semiconductor laser 11c emits light having a maintenance wavelength, for example, wavelength 1650 nm.

Light of the wavelength lambda ₁ emitted from the semiconductor laser 11a is incident to the WDM coupler 13 by the lens 12a, via a demultiplexing optical coupler 14 is output from the measurement connectors 6a to the measured optical fiber 7a. Also, light of the wavelength lambda ₂ emitted from the semiconductor laser 11b, the lens 12b is incident to the WDM coupler 13, through a demultiplexing optical coupler 14 is output from the measurement connectors 6a to the measured optical fiber 7a. The semiconductor laser 11a and the semiconductor laser 11b can be switched as necessary, and light emitted from any one of the semiconductor lasers 11a and 11b can be incident on the optical fiber 7a to be measured.

  The light output to the optical fiber 7a to be measured is reflected at the breaking point (or connection point) of the optical fiber 7a to be measured and collected by the lens 16 from the measurement connector 6a via the multiplexing / demultiplexing optical coupler 14 and the WDM filter module 15. The light is coupled to the light receiving element 17. The WDM filter module 15 includes a WDM filter and switches an optical path according to the wavelength of light. The WDM filter module 15 has a configuration as shown in FIG. 5, for example. In the WDM filter module 15 shown in FIG. 5, the first terminal 55 a is connected to the measurement connector 6 a, the second terminal 56 a is connected to one end of the multiplexing / demultiplexing optical coupler 19, and the third terminal 54 a is light toward the light receiving element 17. It is arrange | positioned in the position which radiates | emits.

  The WDM filter module 15 converts the communication wavelength band incident on the two-core optical fiber 55 from the first terminal 55a into parallel light by the lens 53, and then reflects the communication wavelength light to provide the maintenance wavelength light. The light is reflected by the transmitted WDM filter 52 and emitted from the second terminal 56 a connected to the two-core optical fiber 56. On the other hand, in the WDM filter module 15, the light in the maintenance wavelength band incident on the two-core optical fiber 55 from the first terminal 55 a is converted into parallel light by the lens 53, and then transmitted through the WDM filter 52. The light is condensed on the optical fiber 54 and emitted from the third terminal 54a.

Returning to the description of FIG. 4, on the other hand, the light having the wavelength λ ₃ emitted from the semiconductor laser 11 c is incident on the multiplexing / demultiplexing optical coupler 19 through the lens 12 c and is measured from the measurement connector 6 b through the BPF module 18. 7b. The BPF module 18 includes a BPF, passes only light in a predetermined wavelength range, and attenuates and blocks transmission of light in other wavelength ranges. For example, the BPF module 18 has a configuration as shown in FIG. Yes. In the BPF module 18 shown in FIG. 6, the first terminal 84a is connected to the other end of the multiplexing / demultiplexing optical coupler 19 (terminal not connected to the WDM module 15), and the second terminal 85a is connected to the measurement connector 6b.

As described above, light of wavelength lambda ₃ emitted from the semiconductor laser 11c is incident to the demultiplexing optical coupler 19 by the lens 12c. The multiplexing / demultiplexing optical coupler 19 multiplexes the maintenance wavelength light emitted from the WDM filter module 15 and the light emitted from the semiconductor laser 11 c, and outputs the combined light to the BPF module 18. The BPF module 18 converts the light incident on the optical fiber 84 from the first terminal 84a into parallel light by the lens 81, and then enters the BPF 82 that transmits the maintenance wavelength light and reflects the communication wavelength light. The BPF 82 reflects light in the communication wavelength band, but transmits light in the maintenance wavelength band. The light transmitted by the BPF 82 is condensed on the optical fiber 85 by the lens 83 and emitted from the second terminal 85a. Since the second terminal 85a of the BPF module 18 is connected to the measurement connector 6b, the maintenance wavelength light emitted from the second terminal 85a is output to the optical fiber 7b to be measured via the measurement connector 6b.

  The light output to the optical fiber 7b to be measured is reflected at the breaking point (or connection point) of the optical fiber 7b to be measured, and passes from the measurement connector 6b through the BPF module 18, the multiplexing / demultiplexing optical coupler 19, and the WDM filter module 15. The light is condensed by the lens 16 and coupled to the light receiving element 17.

  By using such OTDR, the break point position of the optical fibers 7a and 7b to be measured is generated at the break point after the outgoing pulse light is generated in the semiconductor lasers 11a and 11b having the communication wavelength or the semiconductor laser 11c having the maintenance wavelength. It is possible to detect based on the time until the reflected return light reaches the light receiving element 17. At the maintenance wavelength, the BPF module 18 that cuts the communication light is provided so as not to be affected by the communication light, so that it can be operated without affecting the communication quality even during the line operation.

JP 2009-85684 A

  However, the configuration of the conventional bi-directional optical module as shown in FIG. 4 has a complicated configuration in which the light is multiplexed by the multiplexing / demultiplexing optical coupler after passing through the optical separator of the dedicated wavelength. For this reason, there are problems that the number of parts increases and the cost increases, and that the coupling loss of parts due to the large number of parts increases, which adversely affects the performance of the bidirectional optical module.

  Further, since a fusion type optical fiber coupler is generally used as the multiplexing / demultiplexing optical coupler, complicated work such as fusion work of the optical fiber and storage processing of the extra length optical fiber occurs, and the number of work steps in the manufacturing process is increased. Will increase. There is also a problem that it is difficult to reduce the size of the bidirectional optical module. In particular, as shown in FIGS. 5 and 6, the WDM filter module 15 and the BPF module 18 are configured so that the light of the single mode fiber is converted into parallel light by the lens, condensed by the lens through the filter, and incident again on the single mode fiber. It has become. For this reason, a coupling loss due to lens aberration, reflection at the lens end surface, etc. occurs in the order of 0.5 to 1 dB, which has the disadvantage of adversely affecting performance.

  Accordingly, the present invention has been made in view of the above problems, and an object of the present invention is to provide a new and improved bidirectional light that has high light output and high sensitivity and can be miniaturized. It is to provide a module and an optical pulse tester.

In order to solve the above problems, according to an aspect of the present invention, there is provided a bidirectional optical module in which light is emitted to an optical fiber and return light is incident from the optical fiber. In the bidirectional optical module, a plurality of light emitting elements that emit light of different wavelengths that are incident on an optical fiber, a light receiving element that receives light emitted from the optical fiber, and a first optical fiber are connected to each other. A wavelength filter defining a wavelength range of light incident on the first port and the second port, a beam splitter for branching the incident light into a plurality of lights, Light emitted from at least one of the light emitting elements and incident on the beam splitter is branched and incident on at least one of the first port and the second port, and incident on the beam splitter. The split beam returned from each optical fiber connected to the first port and the second port is made to split and enter the light receiving element. When provided with a wavelength filter and a beam splitter, the light emitted from the plurality of light emitting elements and said Rukoto provided in the space light while coupling to the optical fiber.

  The bidirectional optical module according to the present invention is configured by arranging a wavelength filter and a beam splitter in the spatial light while the light emitted from a plurality of light emitting elements is coupled to the optical fiber without a complicated configuration. ing. Thereby, since the number of optical fibers can be reduced, it is possible to reduce the fusion work and the fiber forming process, and it is not necessary to secure the bending radius of the fiber, so that the module can be reduced in size. .

  The wavelength filter is provided between the first port and the beam splitter, transmits a light having a wavelength incident on the first port, and blocks a light having a wavelength incident on the second port. A second wavelength filter provided between the filter, the second port and the beam splitter, which transmits light having a wavelength incident on the second port and blocks light having a wavelength incident on the first port; It can also consist of.

  At this time, for example, a multiplexing / demultiplexing filter or a bandpass filter may be used as the first wavelength filter and the second wavelength filter.

  Alternatively, a wavelength filter is provided between the beam splitter and the first port and the second port so that light having a wavelength incident on the first port travels toward the first port and is directed to the second port. You may make it make the light of the wavelength to inject travel toward a 2nd port.

  At this time, for example, a bandpass filter or a multiplexing / demultiplexing filter may be used as the wavelength filter.

  The bidirectional optical module may be configured such that light in the communication wavelength range is incident on the first port and light having a wavelength outside the communication wavelength range is incident on the second port.

In order to solve the above problems, according to another aspect of the present invention, an optical pulse tester for testing loss characteristics of an optical fiber is provided. Such an optical pulse tester includes a bidirectional optical module that emits light to an optical fiber and receives return light from the optical fiber, and bidirectional light that drives the bidirectional optical module to generate light at a predetermined timing. A signal processing unit that calculates loss characteristics of an optical fiber based on a module driving unit, an electric signal conversion unit that converts light incident on the bidirectional optical module into an electric signal, and an electric signal converted by the electric signal conversion unit A section. In the bidirectional optical module, a plurality of light emitting elements that emit light of different wavelengths that are incident on an optical fiber, a light receiving element that receives light emitted from the optical fiber, and an optical fiber are connected to each other. A wavelength filter defining a wavelength range of light incident on the first port and the second port, and a beam splitter for branching the incident light into a plurality of lights. The light emitted from at least one of the light-emitting elements and incident on the beam splitter is branched and incident on at least one of the first port and the second port, and is incident on the beam splitter. A beam spring that splits the incident return light from each optical fiber connected to the first port and the second port and makes it incident on the light receiving element. Includes data and, a wavelength filter and a beam splitter, characterized Rukoto provided in the space light between the light emitted from the plurality of light emitting elements are coupled to the optical fiber.

  As described above, according to the present invention, it is possible to provide a bidirectional optical module and an optical pulse tester that have high light output and high sensitivity and can be miniaturized.

It is explanatory drawing which shows the structure of the bidirectional | two-way optical module which concerns on the 1st Embodiment of this invention. It is explanatory drawing which shows the structure of the bidirectional | two-way optical module which concerns on the 2nd Embodiment of this invention. It is a block diagram which shows the structure of an optical pulse tester. It is explanatory drawing which shows the structure of the conventional bidirectional | two-way optical module. It is explanatory drawing which shows the example of 1 structure of the conventional WDM filter module. It is explanatory drawing which shows the example of 1 structure of the conventional BPF module.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

<1. First Embodiment>
[Configuration of bidirectional optical module]
First, the configuration of the bidirectional optical module 100 according to the first embodiment of the present invention will be described with reference to FIG. FIG. 1 is an explanatory diagram showing the configuration of the bidirectional optical module 100 according to the present embodiment.

  A bidirectional optical module 100 according to the present embodiment is a bidirectional optical module 100 used for OTDR that can be used for both installation and maintenance, and as shown in FIG. 1, light emitting elements 112, 114, and 116 that emit light. Lenses 122, 124, and 126 for collimating light, lenses 125, 127, and 128 for condensing light, multiplexing / demultiplexing filters 132, 134, and 180, beam splitter 140, BPF 150, and optical fiber 162 and 164, and a light receiving element 170 for sensing light. In the bidirectional optical module 100 of the present embodiment, as shown in FIG. 1, light emitting elements 112, 114, 116, a light receiving element 170, and one ends of optical fibers 162, 164 are arranged around a rectangular plane. . The arrangement of elements and the like shown in FIG. 1 is an example, and the present invention is not limited to such an example.

  The bidirectional optical module 100 according to the present embodiment emits light having a communication wavelength from the light emitting elements 112 and 114. The light emitted from the light emitting elements 112 and 114 is switched in the optical path in the bidirectional optical module 100, is coupled to the optical fiber 164, and is emitted to the optical fiber 7b connected to the measurement connector 6b. The return light from the optical fiber 7 b is emitted into the bidirectional optical module 100 via the optical fiber 164, and the light path is switched to enter the light receiving element 170. The bidirectional optical module 100 emits light having a maintenance wavelength from the light emitting element 116. The light emitted from the light emitting element 116 is switched in the optical path in the bidirectional optical module 100, coupled to the optical fiber 162, and emitted to the optical fiber 7a connected to the measurement connector 6a. The return light from the optical fiber 7 a is emitted into the bidirectional optical module 100 via the optical fiber 162, and the light path is switched to enter the light receiving element 170.

  Hereinafter, each element which comprises the bidirectional | two-way optical module 100 which concerns on this embodiment is demonstrated in detail.

(Light emitting element 112, 114, 116)
The light emitting elements 112, 114, and 116 are elements that emit light incident on an optical fiber, and for example, laser diodes (Laser Diodes) can be used. In the present embodiment, the light emitting elements 112 and 114 each emit light having a different wavelength in the communication wavelength band, and the light emitting element 116 emits light having a wavelength other than the communication wavelength band. The wavelength of light emitted from the light emitting element 112 is λ ₁ , the wavelength of light emitted from the light emitting element 114 is λ ₂ , and the wavelength of light emitted from the light emitting element 116 is λ ₃ . In the present embodiment, the wavelengths λ ₁ and λ ₂ are communication wavelengths, for example, 1310 nm and 1550 nm, respectively. In addition, the wavelength λ ₃ is a maintenance wavelength, for example, 1650nm. For example, as shown in FIG. 1, the light emitting elements 112 and 114 can be arranged so that the light emission directions intersect each other. Further, the light emitting element 116 can be disposed on the same plane as the light emitting element 114 as shown in FIG. The light emitted from each of the light emitting elements 112, 114, and 116 travels straight, and the traveling direction is switched by a member disposed on the optical path.

(Lens 122, 124, 126)
The lenses 122, 124, and 126 are lenses for making light into parallel light, and for example, a collimator lens or the like can be used. The lens 122 makes the light emitted from the light emitting element 112 parallel light, the lens 124 makes the light emitted from the light emitting element 114 parallel light, and the lens 126 makes the light emitted from the light emitting element 116 parallel light.

(Lens 125, 127, 128)
The lenses 125, 127, and 128 are lenses for condensing light, and for example, plano-convex lenses can be used. The lens 125 collects the light that has passed through the BPF 150 and couples it to the optical fiber 162. The lens 127 collects the light that has passed through the multiplexing / demultiplexing filter 180 and couples it to the optical fiber 164. The lens 128 collects the return light from the optical fibers 162 and 164 reflected by the beam splitter 140 and couples it to the light receiving element 170.

(Multiplexing filter 132, 134, 180)
The multiplexing / demultiplexing filters 132, 134, and 180 are elements that multiplex or demultiplex incident light. The multiplexing / demultiplexing filter 132 multiplexes the light having the wavelength λ ₁ emitted from the light emitting element 112 and incident from the first surface and the light having the wavelength λ ₂ emitted from the light emitting element 114 and incident from the second surface. . The light combined by the multiplexing / demultiplexing filter 132 travels to the multiplexing / demultiplexing filter 134 side. The multiplexing / demultiplexing filter 134 passes the light that has been combined by the multiplexing / demultiplexing filter 132 and entered from the first surface, reflects the light having the wavelength λ ₃ that has entered the second surface from the light emitting element 116, and is on the beam splitter 140 side. To proceed.

Further, the multiplexing / demultiplexing filter 180 passes the light of the wavelengths λ ₁ and λ ₂ combined by the multiplexing / demultiplexing filter 132 that has passed through the beam splitter 140 described later and entered the first surface, and passes through the optical fiber 164. The return light from the optical fiber 164 incident on the second surface is allowed to pass, and is advanced to the beam splitter 140 side. The multiplexing / demultiplexing filter 180 is one of wavelength filters having a characteristic of reflecting light having a wavelength λ ₃ that is a maintenance wavelength. Instead of the multiplexing / demultiplexing filter 180, a BPF that transmits only light in the communication wavelength range may be used. Thereby, the light of a maintenance wavelength can be interrupted | blocked reliably. Further, the multiplexing / demultiplexing filter 180 may be arranged with an inclination of several degrees (for example, 4 to 5 °) with respect to the optical axis. Thereby, it is possible to reduce the incidence of reflected light directly on the light receiving element 170 and to improve the crosstalk characteristics. Also, the return loss can be improved.

(Beam splitter 140)
The beam splitter 140 is an optical element that divides a light beam into a plurality of parts. A part of the light incident on the beam splitter 140 is reflected and a part of the light is transmitted. As the beam splitter 140, for example, a half mirror having a branching ratio of 50:50 using a dielectric multilayer film can be used. Thereby, the beam splitter 140 transmits 50% of the incident light and reflects 50% of the light. Of the light incident from the first surface of the beam splitter 140, the light transmitted through the beam splitter 140 proceeds to the multiplexing / demultiplexing filter 180 side, and the light reflected by the beam splitter 140 proceeds to the BPF 150 side. Of the light incident from the second surface of the beam splitter 140, the light transmitted through the beam splitter 140 travels to the multiplexing / demultiplexing filter 134 side, and the light reflected by the beam splitter 140 travels to the light receiving element 170 side. To do.

(BPF150)
The BPF 150 is an element that can pass only light in a predetermined wavelength range. The BPF 150 of the present embodiment is one of wavelength filters having a characteristic capable of passing only light in a wavelength range used as a maintenance wavelength. Therefore, the BPF 150 transmits the light having the maintenance wavelength λ ₃ that has been reflected by the beam splitter 140 and travels to the optical fiber 162 side. On the other hand, the wavelengths λ ₁ and λ ₂ that are communication wavelengths are blocked by the BPF 150 and are not incident on the optical fiber 162. The BPF 150 is disposed with an inclination of several degrees (for example, 4 to 5 °) with respect to the optical axis.

(Optical fibers 162, 164)
The optical fibers 162 and 164 are provided to connect the bidirectional optical module 100 to the optical fibers 7a and 7b to be measured. One end of the optical fiber 162 is provided at a position where light is coupled by the lens 125, and the other end is connected to the measurement connector 6a. As a result, light of a predetermined wavelength can be incident on the measured optical fiber 7 a from the bidirectional optical module 100, and return light from the measured optical fiber 7 a can be incident on the bidirectional optical module 100. One end of the optical fiber 162 to which light is coupled by the lens 125 is a port connected to the measured optical fiber 7a.

  Similarly, one end of the optical fiber 164 is provided at a position where light is coupled by the lens 127, and the other end is connected to the measurement connector 6b. As a result, light having a predetermined wavelength can be incident on the measured optical fiber 7 b from the bidirectional optical module 100, and return light from the measured optical fiber 7 b can be incident on the bidirectional optical module 100. One end of the optical fiber 164 to which light is coupled by the lens 127 is a port connected to the measured optical fiber 7b.

(Light receiving element 170)
The light receiving element 170 is an element that senses light. For example, an avalanche photodiode (hereinafter, referred to as “APD”) can be used. The APD is a light receiving element that utilizes the avalanche amplification effect, and can detect weak light with high sensitivity. For this reason, APD (especially APD with a small aperture) is suitable for a light receiving element such as OTDR that must detect weak return light with high distance resolution.

  In such a bidirectional optical module 100, as shown in FIG. 1, the light receiving element 112, the lens 122, the multiplexing / demultiplexing filters 132 and 134, the beam splitter 140, the multiplexing / demultiplexing filter 180, and the lens 127 are arranged on the same straight line (straight line C). ) Is placed on top. In addition, the multiplexing / demultiplexing filter 132, the lens 124, and the light emitting element 114 are arranged on a straight line in a direction orthogonal to the straight line C, and the multiplexing / demultiplexing filter 134, the lens 126, and the light emitting element 116 are arranged on a straight line. Has been. Further, the lens 125, the BPF 150, the beam splitter 140, the lens 128, and the light receiving element 170 are also arranged on the same straight line extending in a direction orthogonal to the straight line C. The lens 125 and the BPF 150 are disposed on the side different from the lens 128 and the light receiving element 170 with respect to the beam splitter 140.

  Thus, in the bidirectional optical module 100, in the spatial light until the light emitted from the light emitting elements 112, 114, 116 is coupled to the two ports connected to the measured optical fibers 7a, 7b, Elements constituting this module are arranged.

[Operation of optical pulse tester with bidirectional optical module]
Next, the function of the bidirectional optical module 100 according to the present embodiment will be described together with the operation of the optical pulse tester including the bidirectional optical module 100. Here, the configuration of the optical pulse tester is the same as that in FIG. 3, and it is assumed that the bidirectional optical module 100 according to the present embodiment is applied instead of the bidirectional optical module 1.

  In the optical pulse tester according to the present embodiment, first, the pulse width of pulsed light is set in advance for the LD drive unit 2 by the signal processing unit 4 of the optical pulse tester OTDR. Next, a timing signal is transmitted to the LD driving unit 2 at a predetermined interval by a timing generating means (not shown) in the signal processing unit 4. The LD driving unit 2 that has received the timing signal causes the light emitting element 112, the light emitting element 124, or the light emitting element 116 of the bidirectional optical module 100 to output pulsed light so as to be synchronized with the timing signal.

(Measurement by communication wavelength)
First, the case where pulsed light with wavelengths λ ₁ and λ ₂ that are communication wavelengths is emitted from the light emitting elements 112 and 114 will be described. The pulsed light with wavelength λ ₁ emitted from the light emitting element 112 is collimated by the lens 122. And enters the first surface of the multiplexing / demultiplexing filter 132. Further, the pulsed light having the wavelength λ ₂ emitted from the light emitting element 114 is converted into parallel light by the lens 124 and is incident on the second surface of the multiplexing / demultiplexing filter 132. The multiplexing / demultiplexing filter 132 multiplexes the parallel lights incident from the first surface and the second surface, and advances them to the multiplexing / demultiplexing filter 134 side.

The multiplexing / demultiplexing filter 134 has a characteristic of transmitting light with wavelengths λ ₁ and λ ₂ that are communication wavelengths and reflecting light with wavelength λ ₃ that is a maintenance wavelength. Therefore, the light combined by the multiplexing / demultiplexing filter 132 travels to the beam splitter 140. The beam splitter 140 transmits a part of the incident light and advances it to the multiplexing / demultiplexing filter 180 side, reflects the other part and advances it to the BPF 150 side. The light transmitted through the beam splitter 140 and incident on the multiplexing / demultiplexing filter 180 has a wavelength λ which is the communication wavelength due to the characteristics of the multiplexing / demultiplexing filter 180 having the characteristic of transmitting the communication wavelength light and reflecting the maintenance wavelength light. Only light of ₁ and λ ₂ is transmitted and condensed by the lens 127 at one end (port) of the optical fiber 164. In this way, the light of the communication wavelength is coupled to the optical fiber 164 and is incident on the measured optical fiber 7b connected to the optical fiber 164.

On the other hand, the light reflected by the beam splitter 140 and incident on the BPF 150 transmits only the light in the maintenance wavelength range, and the wavelength λ ₃ which is the maintenance wavelength due to the characteristics of the BPF 150 having the characteristics of reflecting the other wavelengths. Is transmitted through the lens 125 and condensed on one end of the optical fiber 162 by the lens 125. Therefore, even if the light of the wavelengths λ ₁ and λ ₂ emitted from the light emitting elements 112 and 114 is reflected by the beam splitter 140 and travels toward the optical fiber 162 to which the measured optical fiber 7a is connected, it is reflected by the BPF 150. Therefore, it is not incident on the optical fiber 162.

The light having the wavelengths λ ₁ and λ ₂ incident on the measured optical fiber 7b is reflected at the breaking point of the measured line. This return light enters the bidirectional optical module 100 through the optical fiber 164, is converted into parallel light again by the lens 127, and then enters the second surface of the beam splitter 140. The beam splitter 140 reflects a part of the return light and advances it to the light receiving element 170 side. The return light reflected by the beam splitter 140 is coupled to the light receiving element 170 by the lens 128. When the return light is received by the light receiving element 170 in this way, the sampling unit 3 converts the electrical signal (photocurrent) from the light receiving element 170 of the bidirectional optical module 100 into a voltage and samples it. Then, the signal processing unit 4 performs calculation processing of the electrical signal as a sampling result, and the calculation processing result is displayed on the display unit 5. In this way, an optical time domain reflection point measurement device (OTDR) that measures the break point position of the measured path of the measured optical fiber 7b and the line loss can be configured.

(Measurement by maintenance wavelength)
Next, a case where pulsed light having a wavelength λ ₃ that is a maintenance wavelength is emitted from the light emitting element 116 will be described. The pulsed light having the wavelength λ ₃ emitted from the light emitting element 116 is converted into parallel light by the lens 126 and is incident on the second surface of the multiplexing / demultiplexing filter 134. The multiplexing / demultiplexing filter 132 reflects the parallel light having the wavelength λ ₃ incident from the second surface and advances it to the beam splitter 140 side. The beam splitter 140 transmits part of the incident light and proceeds to the multiplexing / demultiplexing filter 180 side while reflecting the other part and proceeds to the BPF 150 side, as in the case of the measurement using the communication wavelength described above. .

The light transmitted through the beam splitter 140 and incident on the multiplexing / demultiplexing filter 180 has a wavelength λ which is the communication wavelength due to the characteristics of the multiplexing / demultiplexing filter 180 having the characteristic of transmitting the communication wavelength light and reflecting the maintenance wavelength light. Only the light of ₁ and λ ₂ is transmitted and condensed by the lens 127 onto one end of the optical fiber 164. Therefore, even if the light of wavelength λ ₃ emitted from the light emitting element 116 is reflected by the beam splitter 140 and travels toward the optical fiber 164 to which the optical fiber 7b to be measured is connected, it is not incident on the optical fiber 164.

On the other hand, the light reflected by the beam splitter 140 and incident on the BPF 150 transmits only the light in the maintenance wavelength range, and the wavelength λ ₃ which is the maintenance wavelength due to the characteristics of the BPF 150 having the characteristics of reflecting the other wavelengths. Is transmitted through the lens 125 and collected by the lens 125 at one end (port) of the optical fiber 162. Therefore, the light of wavelength λ ₃ emitted from the light emitting element 116 is coupled to the optical fiber 162 and is incident on the measured optical fiber 7 a connected to the optical fiber 162. Since only the maintenance wavelength light is output from the fiber 7a and no communication wavelength light is output, the fiber 7a can be operated without adversely affecting the communication quality even during line operation.

The light of wavelength λ ₃ incident on the measured optical fiber 7a is reflected at the break point of the measured line. The return light enters the bidirectional optical module 100 through the optical fiber 162, is converted into parallel light again by the lens 125, and then enters the first surface of the beam splitter 140. The beam splitter 140 transmits a part of the return light and advances it to the light receiving element 170 side. The return light transmitted by the beam splitter 140 is coupled to the light receiving element 170 by the lens 128. The light having the communication wavelengths λ ₁ and λ ₂ incident on the line and incident from the measured optical fiber 7 a is blocked by the BPF 150. Thus, when the light receiving element 170 receives the return light having the maintenance wavelength λ ₃ , the sampling unit 3 converts the electrical signal (photocurrent) from the light receiving element 170 of the bidirectional optical module 100 into a voltage and samples it. Then, the signal processing unit 4 performs calculation processing of the electrical signal as a sampling result, and the calculation processing result is displayed on the display unit 5. In this way, an optical time domain reflection point measuring device (OTDR) that measures the break point position and the line loss of the measured path of the measured optical fiber 7a can be configured.

  As described above, by using the bidirectional optical module 100 according to the present embodiment in the optical pulse tester OTDR, it is possible to use light having a maintenance wavelength different from the actual communication wavelength band, and communication quality even during line operation. Maintenance work can be performed without affecting the operation.

  The configuration of the bidirectional optical module 100 according to the present embodiment and the operation of the optical pulse tester OTDR using the same have been described above. The bidirectional optical module 100 according to the present embodiment does not have a complicated configuration in which the optical splitter 100 passes through the optical separators of the respective dedicated wavelengths and is multiplexed again by the multiplexing / demultiplexing coupler as in the prior art. 132, 134, 180, the beam splitter 140, and the BPF 150 are arranged in the spatial light of the bidirectional optical module 100. For this reason, since the number of optical fibers can be reduced, it is possible to reduce the fusion work and the fiber forming process, and it is not necessary to secure the bending radius of the fiber, so that the module can be downsized. .

  Furthermore, in the bidirectional optical module 100 according to the present embodiment, like the conventional WDM filter module shown in FIG. 5 and the conventional BPF module shown in FIG. There is no need to adopt a configuration in which light is collimated and further condensed. In addition, since the filters are arranged in the optical system that is made into spatial light because it enters the optical fiber from the light emitting element, each filter loss is about 0.2 dB, and the coupling loss is significantly larger than the configuration shown in FIG. Can be reduced.

  The bidirectional optical module 100 according to the present embodiment is configured to have both a function of allowing light from a light emitting element to enter the fiber and a function of realizing filter characteristics. Thereby, it is not necessary to arrange a lens in order to realize the filter characteristic function, and it is possible to reduce the number of parts and the work process.

<2. Second Embodiment>
[Configuration of bidirectional optical module]
Next, the configuration of the bidirectional optical module 200 according to the second embodiment of the present invention will be described with reference to FIG. FIG. 2 is an explanatory diagram showing the configuration of the bidirectional optical module 200 according to the present embodiment. In the bidirectional optical module 100 according to the first embodiment, the BPF 150 and the multiplexing / demultiplexing filter 180 are disposed between the lenses 125 and 127 that couple light to the optical fibers 162 and 164 and the beam splitter 140, respectively. In the bidirectional optical module 200 according to the embodiment, the functions of the BPF 150 and the multiplexing / demultiplexing filter 180 are realized by one BPF 250. Hereinafter, differences between the configuration of the bidirectional optical module 200 according to the present embodiment and the bidirectional optical module 100 according to the first embodiment will be mainly described.

  The bidirectional optical module 200 according to the present embodiment is a bidirectional optical module 200 used for OTDR that can be used for both installation and maintenance, and as shown in FIG. 2, light emitting elements 212, 214, and 216 that emit light. Lenses 222, 224, 226 for collimating light, lenses 225, 227, 228 for condensing light, multiplexing / demultiplexing filters 232, 234, beam splitter 240, BPF 250, optical fiber 262, H.264 and a light receiving element 270 that senses light. In the bidirectional optical module 200 of the present embodiment, as shown in FIG. 2, light emitting elements 212, 214, 216, a light receiving element 270, and one ends of optical fibers 262, 264 are arranged around a rectangular plane. . The arrangement of elements and the like illustrated in FIG. 2 is an example, and the present technology is not limited to such an example.

  Similarly to the first embodiment, the bidirectional optical module 200 according to the present embodiment emits light having a communication wavelength from the light emitting elements 212 and 214. The light emitted from the light emitting elements 212 and 214 is switched in the optical path in the bidirectional optical module 200, coupled to the optical fiber 264, and emitted to the optical fiber 7b connected to the measurement connector 6b. The return light from the optical fiber 7 b is emitted into the bidirectional optical module 200 via the optical fiber 264, and the light path is switched to enter the light receiving element 270. In addition, the bidirectional optical module 200 emits light having a maintenance wavelength from the light emitting element 216. The light emitted from the light emitting element 216 is switched in the optical path in the bidirectional optical module 200, is coupled to the optical fiber 262, and is emitted to the optical fiber 7a connected to the measurement connector 6a. The return light from the optical fiber 7 a is emitted into the bidirectional optical module 200 via the optical fiber 262, and is incident on the light receiving element 270 after switching the optical path.

  Hereinafter, each element which comprises the bidirectional | two-way optical module 200 which concerns on this embodiment is demonstrated in detail.

(Light emitting elements 212, 214, 216)
The light emitting elements 212, 214, and 216 are elements that emit light incident on an optical fiber, and are configured in the same manner as the light emitting elements 112, 114, and 116 according to the first embodiment using, for example, a laser diode. can do. In the present embodiment, the light emitting elements 212 and 214 each emit light having a different wavelength in the communication wavelength band, and the light emitting element 216 emits light having a wavelength other than the communication wavelength band. The wavelength of light emitted from the light emitting element 212 is λ ₁ , the wavelength of light emitted from the light emitting element 214 is λ ₂ , and the wavelength of light emitted from the light emitting element 216 is λ ₃ . Also in the present embodiment, as in the first embodiment, the wavelengths λ ₁ and λ ₂ are communication wavelengths, and the wavelength λ ₃ is a maintenance wavelength. For example, as shown in FIG. 2, the light emitting elements 212 and 214 can be arranged so that the light emission directions intersect each other. Further, the light emitting element 216 can be arranged on the same plane as the light emitting element 214 as shown in FIG. The light emitted from each of the light emitting elements 212, 214, and 216 travels straight, and the traveling direction is switched by a member disposed on the optical path.

(Lens 222, 224, 226)
The lenses 222, 224, and 226 are lenses for making light into parallel light, and can be configured similarly to the lenses 122, 124, and 126 according to the first embodiment using, for example, a collimator lens. The lens 222 makes the light emitted from the light emitting element 212 parallel light, the lens 224 makes the light emitted from the light emitting element 214 parallel light, and the lens 226 makes the light emitted from the light emitting element 216 parallel light.

(Lens 225, 227, 228)
The lenses 225, 227, and 228 are lenses for collecting light, and can be configured in the same manner as the lenses 125, 127, and 128 according to the first embodiment using, for example, plano-convex lenses. The lens 225 collects the light reflected by the BPF 250 and couples it to the optical fiber 262. The lens 227 collects the light that has passed through the BPF 250 and couples it to the optical fiber 264. The lens 228 collects the return light from the optical fibers 262 and 264 reflected by the beam splitter 240 and couples it to the light receiving element 270.

(Multiplexing filter 232, 234)
The multiplexing / demultiplexing filters 232 and 234 are elements that multiplex or demultiplex incident light. The multiplexing / demultiplexing filter 232 multiplexes the light having the wavelength λ ₁ emitted from the light emitting element 212 and incident from the first surface and the light having the wavelength λ ₂ emitted from the light emitting element 214 and incident from the second surface. . The light combined by the multiplexing / demultiplexing filter 232 travels to the multiplexing / demultiplexing filter 234 side. The multiplexing / demultiplexing filter 234 passes the light that has been combined by the multiplexing / demultiplexing filter 232 and entered from the first surface, reflects the light of wavelength λ ₃ that has entered the second surface from the light emitting element 216, and is on the beam splitter 240 side To proceed.

(Beam splitter 240)
The beam splitter 240 is an optical element that divides a light beam into a plurality of parts. A part of the light incident on the beam splitter 240 is reflected and a part of the light is transmitted. As the beam splitter 240, for example, a half mirror having a branching ratio of 50:50 using a dielectric multilayer film can be used, as in the first embodiment. As a result, the beam splitter 240 transmits 50% of the incident light and reflects 50% of the light. Of the light incident from the first surface of the beam splitter 240, the light transmitted through the beam splitter 240 travels to the BPF 250 side. Of the light incident from the second surface of the beam splitter 240, the light transmitted through the beam splitter 240 travels to the multiplexing / demultiplexing filter 234 side, and the light reflected by the beam splitter 240 travels to the light receiving element 270 side. To do.

(BPF250)
The BPF 250 is an element that can pass only light in a predetermined wavelength range. The BPF 250 of this embodiment has a characteristic that allows only light in a wavelength range used as a communication wavelength to pass. Therefore, the BPF 250 reflects the light having the wavelength λ ₃ that has been transmitted through the beam splitter 240 and is out of the use range used as the communication wavelength, and proceeds to the optical fiber 262 side. On the other hand, since the wavelengths λ ₁ and λ ₂ are within the wavelength range used as the communication wavelengths, the BPF 250 passes the light of the wavelengths λ ₁ and λ ₂ and advances the light toward the optical fiber 264 side.

(Optical fibers 262, 264)
The optical fibers 262 and 264 are provided to connect the bidirectional optical module 200 to the optical fibers 7a and 7b to be measured. One end of the optical fiber 262 is provided at a position where the light is coupled by the lens 225, and the other end is connected to the measurement connector 6a. As a result, light of a predetermined wavelength can be made incident on the measured optical fiber 7 a from the bidirectional optical module 200, and return light from the measured optical fiber 7 a can be made incident on the bidirectional optical module 200. One end of the optical fiber 262 to which light is coupled by the lens 225 is a port connected to the measured optical fiber 7a.

  Similarly, one end of the optical fiber 264 is provided at a position where light is coupled by the lens 227, and the other end is connected to the measurement connector 6b. As a result, light having a predetermined wavelength can be incident on the measured optical fiber 7 b from the bidirectional optical module 200, and return light from the measured optical fiber 7 b can be incident on the bidirectional optical module 200. The optical fibers 262 and 264 can be configured in the same manner as the optical fibers 162 and 164 of the first embodiment. One end of the optical fiber 264 to which light is coupled by the lens 227 is a port connected to the measured optical fiber 7b.

(Light receiving element 270)
The light receiving element 170 is an element that senses light. For example, an APD can be used as in the light receiving element 170 of the first embodiment. The light receiving element 170 receives the return light from the measured optical fibers 7a and 7b that is incident on the beam splitter 240 and reflected.

  As shown in FIG. 2, in the bidirectional optical module 200, the light receiving element 212, the lens 222, the multiplexing / demultiplexing filters 232 and 234, the beam splitter 240, the BPF 250, and the lens 227 are arranged on the same straight line (straight line C). . Further, in the direction orthogonal to the straight line C, the multiplexing / demultiplexing filter 132, the lens 224, and the light emitting element 214 are arranged on a straight line, and the multiplexing / demultiplexing filter 234, the lens 226, and the light emitting element 216 are arranged on a straight line. Has been. Further, the beam splitter 240, the lens 228, and the light receiving element 270 are also arranged on the same straight line extending in the direction orthogonal to the straight line C, and the lens 225 and the BPF 250 are also the same straight line extending in the direction orthogonal to the straight line C. It is arranged on the line. The lens 225 is disposed on the side different from the light receiving element 270 and the like with respect to the straight line C.

  As described above, in the bidirectional optical module 200, the light emitted from the light emitting elements 212, 214, and 216 is included in the spatial light until the light is coupled to the two ports connected to the optical fibers to be measured 7a and 7b. Elements constituting this module are arranged.

[Operation of optical pulse tester with bidirectional optical module]
Next, the function of the bidirectional optical module 200 according to the present embodiment will be described together with the operation of the optical pulse tester including the bidirectional optical module 200. Here, the configuration of the optical pulse tester is the same as in FIG. 3, and it is assumed that the bidirectional optical module 200 according to the present embodiment is applied instead of the bidirectional optical module 1.

  As in the optical pulse tester OTDR according to the first embodiment, the optical pulse tester according to the present embodiment is first preliminarily pulsed with respect to the LD drive unit 2 by the signal processing unit 4 of the optical pulse tester OTDR. Sets the pulse width of light. Next, a timing signal is transmitted to the LD driving unit 2 at a predetermined interval by a timing generating means (not shown) in the signal processing unit 4. The LD driving unit 2 that has received the timing signal causes the light emitting element 212, the light emitting element 224, or the light emitting element 216 of the bidirectional optical module 100 to output pulsed light so as to be synchronized with the timing signal.

(Measurement by communication wavelength)
First, the case where pulsed light with wavelengths λ ₁ and λ ₂ that are communication wavelengths is emitted from the light emitting elements 212 and 214 will be described. The pulsed light with wavelength λ ₁ emitted from the light emitting element 212 is collimated by the lens 222. And enters the first surface of the multiplexing / demultiplexing filter 232. Further, the pulsed light having the wavelength λ ₂ emitted from the light emitting element 214 is converted into parallel light by the lens 224 and is incident on the second surface of the multiplexing / demultiplexing filter 232. The multiplexing / demultiplexing filter 232 multiplexes the parallel lights incident from the first surface and the second surface, and proceeds to the multiplexing / demultiplexing filter 234 side.

The multiplexing / demultiplexing filter 234 has a characteristic of transmitting light having wavelengths λ ₁ and λ ₂ that are communication wavelengths and reflecting light having a wavelength λ ₃ that is a maintenance wavelength. Therefore, the light combined by the multiplexing / demultiplexing filter 232 travels to the beam splitter 240. The beam splitter 240 transmits a part of the incident light and advances it to the BPF 250 side. The light transmitted through the beam splitter 240 and incident on the BPF 250 has a wavelength λ which is a communication wavelength due to the characteristics of the BPF 250 having a characteristic of transmitting light of the communication wavelength range and reflecting light of the maintenance wavelength in the other wavelength range. Only light of ₁ and λ ₂ is transmitted and condensed by the lens 227 to one end (port) of the optical fiber 264. In this way, the light of the communication wavelength is coupled to the optical fiber 264 and is incident on the measured optical fiber 7b connected to the optical fiber 264.

The light having the wavelengths λ ₁ and λ ₂ incident on the measured optical fiber 7b is reflected at the breaking point of the measured line. This return light enters the bidirectional optical module 200 through the optical fiber 264, is converted into parallel light again by the lens 227, and then enters the second surface of the BPF 250. The BPF 250 transmits the return light and advances it to the beam splitter 240 side. A part of the return light incident on the beam splitter 240 is reflected to the light receiving element 270 side and coupled to the light receiving element 270 by the lens 228. Thus, when the return light is received by the light receiving element 270, the sampling unit 3 converts the electrical signal (photocurrent) from the light receiving element 270 of the bidirectional optical module 200 into a voltage and samples it. Then, the signal processing unit 4 performs calculation processing of the electrical signal as a sampling result, and the calculation processing result is displayed on the display unit 5. In this way, an optical time domain reflection point measurement device (OTDR) that measures the break point position of the measured path of the measured optical fiber 7b and the line loss can be configured.

(Measurement by maintenance wavelength)
Next, a case where pulsed light having a wavelength λ ₃ that is a maintenance wavelength is emitted from the light emitting element 216 will be described. The pulsed light having the wavelength λ ₃ emitted from the light emitting element 216 is converted into parallel light by the lens 226 and is incident on the second surface of the multiplexing / demultiplexing filter 234. The multiplexing / demultiplexing filter 232 reflects the parallel light having the wavelength λ ₃ incident from the second surface, and advances it to the beam splitter 240 side. The beam splitter 240 transmits a part of the incident light and advances it to the BPF 250 side as in the case of the measurement using the communication wavelength described above.

The light transmitted through the beam splitter 240 and incident on the BPF 250 is reflected by the characteristics of the BPF 250 having the characteristics of transmitting the light in the communication wavelength range and reflecting the light having the maintenance wavelength outside the communication wavelength range. The light is condensed at one end (port) of the fiber 262. Accordingly, light of the wavelength lambda ₃ emitted from the light emitting element 216 does not proceed to the optical fiber 264 side of the measured optical fiber 7b is connected.

The light of wavelength λ ₃ incident on the measured optical fiber 7a is reflected at the break point of the measured line. The return light enters the bidirectional optical module 200 through the optical fiber 262, is converted into parallel light again by the lens 225, and then enters the first surface of the BPF 250. The BPF 250 reflects the return light and advances it to the beam splitter 240 side. A part of the return light incident on the beam splitter 240 is reflected to the light receiving element 270 side and coupled to the light receiving element 270 by the lens 228. Thus, when the return light is received by the light receiving element 270, the sampling unit 3 converts the electrical signal (photocurrent) from the light receiving element 270 of the bidirectional optical module 200 into a voltage and samples it. Then, the signal processing unit 4 performs calculation processing of the electrical signal as a sampling result, and the calculation processing result is displayed on the display unit 5. In this way, an optical time domain reflection point measurement device (OTDR) that measures the break point position of the measured path of the measured optical fiber 7b and the line loss can be configured.

  As described above, by using the bidirectional optical module 200 according to the present embodiment in the optical pulse tester OTDR, it is possible to use light having a maintenance wavelength different from the actual communication wavelength band, and communication quality even during line operation. Maintenance work can be performed without affecting the operation.

  Similarly to the first embodiment, the bidirectional optical module 200 according to the present embodiment includes the multiplexing / demultiplexing filters 232 and 234, the beam splitter 240, and the BPF 250 without using a complicated configuration as in the related art. The configuration is arranged in 200 spatial lights. For this reason, since the number of optical fibers can be reduced, it is possible to reduce the fusion work and the fiber forming process, and it is not necessary to secure the bending radius of the fiber, so that the module can be downsized. . Further, since the filter is disposed in the optical system that is made into spatial light because it enters the optical fiber from the light emitting element, the coupling loss can be greatly reduced as compared with the configuration shown in FIG.

  Furthermore, since the bidirectional optical module 200 has a function of causing the light-emitting element to enter the fiber and a function of realizing the filter characteristics, there is no need to arrange a lens to realize the filter characteristics function. It is possible to reduce the number of parts and work processes.

  In the bidirectional optical module 200 according to this embodiment, it can be said that the BPF 250 has the functions of the BPF 150 and the multiplexing / demultiplexing filter 180 of the bidirectional optical module 100 according to the first embodiment. Therefore, compared with the first embodiment, the bidirectional optical module 200 according to the present embodiment can reduce the number of parts, and thus can further reduce the work process. Furthermore, the beam splitter 240 reflects part of the light emitted from the light emitting elements 212, 214, and 216 and incident on the beam splitter 240, but no optical element is arranged in the direction in which the light is reflected. In this way, crosstalk characteristics can be improved by allowing reflected light to escape from the wall.

  The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

For example, in the above embodiment, _two specific communication wavelengths of 1310 nm and 1550 nm and a maintenance wavelength of 1650 nm are illustrated as specific examples of the wavelengths λ ₁ , λ ₂ , and λ ₃ of the light emitted from the light emitting element. It is not limited to such an example. For example, the communication wavelength may be only one wavelength of 1310 nm, or may be three wavelengths of 1310 nm, 1490 nm, and 1550 nm. The maintenance wavelength may be a wavelength such as 1625 nm, for example. As described above, the number of wavelengths of emitted light may be increased or decreased by changing the number of light emitting elements of the bidirectional optical module, and the wavelength of the light can be appropriately selected. In this case, an optical element such as a multiplexing / demultiplexing filter or a BPF may be selected that has characteristics according to the wavelength of the selected light.

  In the above embodiment, the multiplexing / demultiplexing filters 132 and 134 have the characteristics of passing short wavelength light and reflecting long wavelength light. However, the present invention is not limited to this example. For example, in the example of FIG. 1, when the arrangement of the light emitting element 1112 and the light emitting element 116 is switched, the characteristic of transmitting the long wavelength light to the multiplexing / demultiplexing filters 132 and 134 and reflecting the short wavelength light. By using what has this, the effect similar to the said embodiment can be acquired.

  Further, in the first embodiment, the BPF 150 has been described as having the characteristic of reflecting the communication wavelength light and transmitting the maintenance wavelength light. However, the present invention is not limited to such an example. Instead, a multiplexing / demultiplexing filter that transmits only the light having the maintenance wavelength may be used.

  In the above-described embodiment, the confocal optical system that converts the lens into parallel light has been described. However, the present invention is not limited to such an example. For example, a single lens system including one lens may be used. The effect of can be obtained.

  Furthermore, in the above-described embodiment, the bidirectional optical module in which the optical element is arranged as illustrated in FIG. 1 or FIG. 2 has been described. However, the present invention is not limited to such an example. For example, the angle of the filter can be changed, It is possible to change the arrangement of the optical elements constituting the bidirectional optical module by changing the angle of the multiplexing / demultiplexing filter by 90 °. For example, in the example shown in FIG. 2, the lens 228 and the light receiving element 270 can be arranged on the same side as the surface on which light is collected by the lens 227. In this case, the reflection angle of the light of the beam splitter 240 is adjusted so that a part of the return light from the measured optical fiber 7b is reflected to the light receiving element 270 side. Further, for example, in the example shown in FIG. 2, the light emitting element 216, the lens 226, the light receiving element 270, and the lens 227 are arranged so as to be located on the opposite side to the light receiving element 214 with respect to the straight line C (that is, on the same side as the lens 225). You can also In this case, the bidirectional optical module can function in the same manner as the bidirectional optical module 200 of FIG. 2 by changing the arrangement of the multiplexing / demultiplexing filter 234 and the beam splitter 240 by 90 ° from the state of FIG. Of course, it is possible to arrange a bidirectional optical module having the features of the present invention by arranging optical elements in a form other than these modified examples.

OTDR Optical pulse tester 2 LD drive unit 3 Sampling unit 4 Signal processing unit 5 Display unit 6a, 6b Measurement connector 7a, 7b Optical fiber under measurement 100, 200 Optical bidirectional module 112, 114, 116, 212, 214, 216 Light emission Element 122, 124, 126, 125, 127, 128, 222, 224, 226, 225, 227, 228 Lens 132, 134, 180, 232, 234 Multiplexing / demultiplexing filter 140, 240 Beam splitter 150, 250 BPF
162, 164, 262, 264 Optical fiber 170, 270 Light receiving element

Claims (7)

A bi-directional optical module that emits light to an optical fiber and receives return light from the optical fiber,
A plurality of light emitting elements that emit light of different wavelengths, which are incident on the optical fiber;
A light receiving element for receiving light emitted from the optical fiber;
A first port and a second port to which the optical fibers are respectively connected;
A wavelength filter defining a wavelength range of light incident on the first port and the second port;
A beam splitter for branching incident light into a plurality of lights, wherein the light emitted from at least one of the plurality of light emitting elements and incident on the beam splitter is branched, and the first port Alternatively, the light is incident on at least one of the second ports, and the return light from the optical fibers connected to the first port and the second port, which is incident on the beam splitter, is branched. A beam splitter that is incident on the light receiving element;
Equipped with a,
Said wavelength filter and the beam splitter is characterized Rukoto provided in the space light between the light emitted from the plurality of light emitting elements are attached to said optical fiber, bi-directional optical module. The wavelength filter is
A first wavelength filter provided between the first port and the beam splitter, which transmits light having a wavelength incident on the first port and blocks light having a wavelength incident on the second port. When,
A second wavelength filter that is provided between the second port and the beam splitter, transmits light having a wavelength incident on the second port, and blocks light having a wavelength incident on the first port. When,
The bidirectional optical module according to claim 1, comprising:   The bidirectional optical module according to claim 2, wherein the first wavelength filter and the second wavelength filter are a multiplexing / demultiplexing filter or a band pass filter. The wavelength filter is
Provided between the beam splitter and the first port and the second port;
Light having a wavelength incident on the first port travels toward the first port, and light having a wavelength incident on the second port travels toward the second port. The bidirectional optical module according to claim 1.   The bidirectional optical module according to claim 4, wherein the wavelength filter is a bandpass filter or a multiplexing / demultiplexing filter. Light in the communication wavelength range is incident on the first port;
The bidirectional optical module according to claim 1, wherein light having a wavelength outside the communication wavelength range is incident on the second port. An optical pulse tester for testing loss characteristics of an optical fiber,
A bidirectional optical module that emits light to the optical fiber and in which return light is incident from the optical fiber;
A bidirectional optical module driving unit that drives the bidirectional optical module to generate light at a predetermined timing;
An electrical signal converter that converts light incident on the bidirectional optical module into an electrical signal;
Based on the electrical signal converted by the electrical signal converter, a signal processor that calculates loss characteristics of the optical fiber;
With
The bidirectional optical module includes:
A plurality of light emitting elements that emit light of different wavelengths, which are incident on the optical fiber;
A light receiving element for receiving light emitted from the optical fiber;
A first port and a second port to which the optical fibers are respectively connected;
A wavelength filter defining a wavelength range of light incident on the first port and the second port;
A beam splitter for branching incident light into a plurality of lights, wherein the light emitted from at least one of the plurality of light emitting elements and incident on the beam splitter is branched, and the first port Alternatively, the light is incident on at least one of the second ports, and the return light from the optical fibers connected to the first port and the second port, which is incident on the beam splitter, is branched. A beam splitter that is incident on the light receiving element;
Equipped with a,
It said wavelength filter and the beam splitter, the plurality of the light emitted from the light emitting element is characterized Rukoto provided in the space light while coupled to the optical fiber, the optical pulse tester.

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